<html>

<head>
       
    <meta charset="UTF-8">
       
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
       
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>Document</title>
</head>

<body>
       
    <script>
        var x;
        console.log(x);
        var str1 = "hello word"
        var str2 = 'hello word'
        console.log(str1)
        console.log(str2)
        var str3 = "小红你真漂亮"
        console.log(str3);
        //字符替换
        var str = "java"
        var str = str + "script"
        console.log(str);
    </script>
</body>

</html>